Jaguar's XF sedan has been given a thrifty 2.2 litre diesel engine for 2012. We couldn't match the factory fuel consumption claim in our review (it's too fun to drive), but a cross-country run in the US has crushed the official 5.4 l/100km figure.

The XF 2.2 isn't offered in the US, so Jaguar shipped a right-hand-drive model over from the UK, running from New York City in the East to Los Angeles on the West coast.

Covering a total distance of 4641 kilometres, the team reports that it managed an average fuel consumption of 3.7 l/100km.

Officially, the XF 2.2 offers a combined-cycle fuel economy of 5.4 l/100km. With the bulk of the US trip covering the continent's vast stretches of non-stop blacktop, it's the 4.8 l/100km Extra Urban figure that really counts in this challenge.

"This project was designed primarily to test the potential economy of the XF 2.2. The incredible figures achieved by the car were accomplished through making every element of the new XF as efficient as possible – from its aerodynamics to its four-cylinder 2.2-litre diesel engine linked to an eight-speed gearbox," XF Project Manager Paul Alcock said.

"The whole XF team is incredibly proud of what's been achieved and it's a graphic demonstration of the strength, engineering integrity and efficiency of the car."

The XF 2.2 is powered by a 2.2 litre diesel engine delivering 140kW and 450Nm of torque, combined with a new eight-speed ZF automatic transmission and stop/start technology.

Wow that is amazing, I would love to get my hands on one of these bad boys. I have an XF 3.0 diesel that according to www.fuelmileage.com.au gets 6.8 L/100km which I have never been able to match. I get closer to 8 but I do a lot of city driving.